In mechanical watches, the source of energy for driving the gear train and the hands, including the date display, is a wound spiral spring in a barrel.
When a mechanical watch is not wound regularly, or a watch with automatic winding has not been worn for several hours, the watch spring relaxes completely and the watch stops. This is all the more disagreeable because not only does the hour display stop, but also the date indication by way of the wheel or wheels of the calendar. The average operational power reserve of a normal watch is completely used up, i.e. when the watch is wound well, in about 40 to 60 hours.
There are several reasons for a watch to discharge its energy until it stops totally. The main reasons are, on the one hand, non-use of the watch (it is left in a box, it is not worn on the weekend, etc.) or just simply one has forgotten to wind it, in the case of non-automatic watches. It is thus highly desirable to have watches provided with an operational power reserve extending beyond that of known watches.
In the past, this flaw with mechanical watches has already been addressed, and a solution sought. For example, Swiss patent No. CH-693155 mentions as aim to increase the power reserve of a timepiece movement by reducing as much as possible the loss of driving torque during the first 24 or 48 hours of operation. This object is achieved by providing two barrels, having equal features, driving alternately the timepiece movement and working in turn with a blocking switch between the two barrels.
European patent application No. EP-11188982.0 (EP 2 455 820) proposes the use of a motor organ comprising a barrel in which two superimposed and coaxial springs are mounted.
These two documents cited above are just examples of watches with two barrels or two springs because there are numerous publications for these proposals. Such proposals for solving the problem of increasing operation are not very interesting because these solutions propose roughly to put in as many barrels, permitting the storage of energy, as power reserve desired. The power reserve is thus increased at the expense of the space available.
Moreover the state of the art remains silent concerning an examination of the distribution of torque in a timepiece movement, i.e. one has not yet discovered where the different energy demands are located in the movement. In contrast, the patent application holder has posed as additional the analysis of the torque, from the barrel to the hands.